1. Field of the Invention
This invention relates generally to prosthetic apparatus and methods, and more particularly to a computerized electronic hand prosthesis apparatus and method utilizing configurable input, feedback, control, and operating systems to transmit feedback signals representing the gripping force back to the wearer in the form of vibratory stimuli which changes in vibratory pattern and amplitude at selective grip forces and allow precise positioning and gripping force control for a specific wearer.
2. Brief Description of the Prior Art
Although the mechanical hand is more acceptable than other prosthetic terminal devices, the problems associated with using a conventional mechanical hand prosthesis limits its usefulness and ultimately affects the wearer's acceptance of the prosthesis.
A person with a conventional mechanical hand prosthesis has the ability to control the grip of an object based only on visual or aural feedback. This is a problem because the wearer must discern the amount of pressure to apply to objects based on the deflection of a surface, the sound of the hand drive motor, or guessing on trial and error. If the grip is too tight, the object may be crushed or break, or, if too light, the object may be dropped. If the wearer is distracted or forgets that the hand is still holding the object, the lack of feedback could create a dangerous or embarrassing situation.
Most conventional electric control systems that drive the mechanical hand are simple designs which allow two conditions, either full speed or off. This makes it difficult for the wearer to accurately position the hand which affects gripping ability.
Conzelman, Jr. et al, U.S. Pat. No. 2,656,545, discloses a prosthetic device having a sensory apparatus for transmitting to the wearer of the artificial device an indication of contact that is made by the artificial member. In one embodiment, a bladder on the end of the finger of the prosthesis is connected by a flexible tube to a second bladder held by a harness to a normally sensitive part of the skin of the stump of the amputee. In another embodiment, a switch on the end of the finger of the prosthesis closes an electrical circuit in response to finger tip pressure and a vibrator disc held by a harness to a normally sensitive part of the skin vibrates in intensity relative to the finger tip pressure.
Patterson et al, U.S. Pat. No. 4,808,187, discloses a tactile stimulus receptor for use with a myoelectric prosthesis having a piezoelectric transducer positioned on the gripping fingers of the prosthesis which senses pressure resulting from gripping and converts the sensed pressure into electrical signals proportional to the pressure to a hydraulic motor and cylinder which is connected by a tube to a pressurizable cuff mounted on the wearer's forearm. The cuff constricts the forearm upon increased pressurization and reduces constriction upon reduced pressurization.
Fletcher et al, U.S. Pat. No. 3,751,733, discloses a prosthetic device including a socket for mounting the frame of the device on the stump of the amputee. A piezoelectric transducer and a temperature transducer are provided in flexible digits of the hand for sensing pressure and temperature. The transducers detect tactile stimuli and are connected through a power circuit to a pair of solenoids and a resistance heating element supported by a strap buckled about the stump. Tactile stimuli detected at the sensing devices are reproduced and applied to the skin of the appendage as a pinching and heating or cooling sensation for stimulating sensory organs.
Barry, U.S. Pat. No. 4,571,750, discloses the use of acoustic signals generated by muscles during contraction to generate signals responsive to muscle activity. The invention relates to a complex method of analyzing a human body and controlling prosthetic devices which use acoustic signals obtained from skeletal muscles alone and in combination with myoelectric signals.
Barkhordar et al, U.S. Pat. No. 4,650,492, relates to an artificial hand that comprise a palm member and thumb and finger members movable by an actuator. A microphone is used to pick up pressure waves resulting from a stick/slip motion of the object being picked up along the surface of the hand.
Giampapa, U.S. Pat. No. 4,770,662, discloses sonic frequency generators in electrical communication with pressure transducers in the digits of an artificial hand. Output signals in the form of voltage and sonic frequency are transferred to a bone stump and transmitted to the brain via the spinal column.
The present invention is distinguished over the prior art in general, and these patents in particular by a computerized electronic hand prosthesis apparatus and method utilizing input, feedback, control, and operating systems configurable to provide precise control and gripping forces corresponding to the particular capabilities and requirements of an individual wearer. An articulated prosthesis capable of exerting a mechanical gripping force contains a programmable microcomputer. Electrodes on the prosthesis contact muscles of the remnant portion of a limb and produce an electric command signal responsive to the myoelectric signal created by the wearer contracting and relaxing the muscles in the remnant portion. A drive motor in the prosthesis causes the prosthesis to exert a mechanical gripping force responsive and proportional to the electric command signal. Force sensors in the digits of the prosthesis detect the force exerted and produce an electric sensor signal responsive and proportional thereto. A motor driven vibratory device on the prosthesis engages the remnant portion of the limb adjacent sensory nerves and produces a feedback signal perceptible to the wearer which changes in vibratory pattern and amplitude at various selective grip forces. A communication port on the prosthesis is releasably connected to peripheral devices for exchanging data, diagnosing, correcting, or setting the operational parameters of the prosthesis. The electrodes, drive motor, force sensors, vibratory device, and communication port are controlled by the microcomputer.